1. Field of the Invention
The present invention relates to characterizing and classifying a pose in low dimension.
2. Description of Background Art
A human pose is a unique configuration of the body. A pose can be described by a θ, an n×1 vector of configuration variables, usually the joint angles. With knowledge of the limb segment geometry (e.g., the shapes and sizes of the limb segments) and the types of joints involved, which are all constants for a particular human model, θ can describe the pose. To completely describe a human pose, n may need to be as high as 40.
FIG. 1 illustrates representations of a human pose in high-dimensional and low-dimensional space. θ can be represented in an n-dimensional space spanned by the configuration variables (here, joint angles) and referred to as the joint space, illustrated at the left of FIG. 1. Each point in the joint space represents a unique pose. A range of similar poses is represented as a cluster of points. For example, a number of different standing poses is represented by the “Stand” cluster. As mentioned above, n may need to be as high as 40, making the joint space a very high dimension space. As a result, analysis in this space, including automated characterization and classification of human poses, can be difficult.
Human poses can also be represented in a low-dimensional space as illustrated on the right side of FIG. 1. This low-dimensional space is often called a “feature space” indicating that the space is spanned by a small number of features associated with the pose. The illustrated feature space is a three dimensional space containing the same poses as the joint space. Identical poses in the two spaces are connected by dotted lines. Analysis and visualization of poses can be improved when the poses are represented in a low-dimensional feature space. Classification and recognition problems become simpler.
What is needed is a method for representing a human poses in a low-dimensional space in a way that allows for efficient characterization and classification of the pose.